I share some of Pete's concerns about this proposed measurement technique; however, I don't agree with all of his points.
I do not see the significance of what happens from one season to the next since, as I understand the method, the data used were all gathered on the same day. Pressure and circumference are taken at the start of calibration and throughout the day until post-measurement calibration.
Perhaps a compromise on this issue would be to allow the method to be used but still require a post-measurement calibration (PMC). In this way readings would have been taken before calibration, before and after each ride, and before PMC. In my opinion this would result in a more accurate measurement as it would adjust wheel circumference during the mesurement procedure to assure that the constant remains more valid.
It can be very difficult to find a suitable site for laying out a calibration course in some areas (more because the potential of parked cars on a straight stretch of road)and a helper is not always available. While it can be done solo, it is very time consuming and has a greater potntial for calculation errors since there are more calculations. The other question I always have when using race personnel to help lay out a calibration course is what exactly is the person on the other end of the tape doing?
My personal experience shows one example where this system would have been very helpful. I measured a 5 km course about 70 miles from home, using my home calibration course. The weather was fairly constant up until the PMC. While driving home, the temperature dropped and there was a heavy rain. Consequently I encountered a higher PMC constant requiring adjustment of 8' to the course. As I understand Neville's system, this need for course adjustment would not have been necessary since I would have adjusted pressure (and therefore circumference) prior to my PMC.
The biggest potential problem I see with this method is variation in equipment and the competence of the person using the technique.
As a certifier, I have less concern with understanding what has been done with this system than I do with someone who is new to the system using the electronic counter system (perhaps this is due to the fact that I have yet to try the electronic system).
As a final note, I too applaud Neville for his continuing quest to make our task easier and more accurate. Nothing was ever improved without someone "pushing the envelope".
Paul Hronjak
hronjak@simflex.com